The challenges of statistical patterns of language: the case of Menzerath's law in genomes

The importance of statistical patterns of language has been debated over decades. Although Zipf's law is perhaps the most popular case, recently, Menzerath's law has begun to be involved. Menzerath's law manifests in language, music and genomes as a tendency of the mean size of the parts to decrease as the number of parts increases in many situations. This statistical regularity emerges also in the context of genomes, for instance, as a tendency of species with more chromosomes to have a smaller mean chromosome size. It has been argued that the instantiation of this law in genomes is not indicative of any parallel between language and genomes because (a) the law is inevitable and (b) non-coding DNA dominates genomes. Here mathematical, statistical and conceptual challenges of these criticisms are discussed. Two major conclusions are drawn: the law is not inevitable and languages also have a correlate of non-coding DNA. However, the wide range of manifestations of the law in and outside genomes suggests that the striking similarities between non-coding DNA and certain linguistics units could be anecdotal for understanding the recurrence of that statistical law.Comment: Title changed, abstract and introduction improved and little corrections on the statistical argument

The infochemical core

Vocalizations, and less often gestures, have been the object of linguistic research for decades. However, the development of a general theory of communication with human language as a particular case requires a clear understanding of the organization of communication through other means. Infochemicals are chemical compounds that carry information and are employed by small organisms that cannot emit acoustic signals of an optimal frequency to achieve successful communication. Here, we investigate the distribution of infochemicals across species when they are ranked by their degree or the number of species with which they are associated (because they produce them or are sensitive to them). We evaluate the quality of the fit of different functions to the dependency between degree and rank by means of a penalty for the number of parameters of the function. Surprisingly, a double Zipf (a Zipf distribution with two regimes, each with a different exponent) is the model yielding the best fit although it is the function with the largest number of parameters. This suggests that the worldwide repertoire of infochemicals contains a core which is shared by many species and is reminiscent of the core vocabularies found for human language in dictionaries or large corpora.Peer ReviewedPostprint (author's final draft

Compression as a universal principle of animal behavior

A key aim in biology and psychology is to identify fundamental principles underpinning the behavior of animals, including humans. Analyses of human language and the behavior of a range of non-human animal species have provided evidence for a common pattern underlying diverse behavioral phenomena: words follow Zipf's law of brevity (the tendency of more frequently used words to be shorter), and conformity to this general pattern has been seen in the behavior of a number of other animals. It has been argued that the presence of this law is a sign of efficient coding in the information theoretic sense. However, no strong direct connection has been demonstrated between the law and compression, the information theoretic principle of minimizing the expected length of a code. Here we show that minimizing the expected code length implies that the length of a word cannot increase as its frequency increases. Furthermore, we show that the mean code length or duration is significantly small in human language, and also in the behavior of other species in all cases where agreement with the law of brevity has been found. We argue that compression is a general principle of animal behavior, that reflects selection for efficiency of coding.Comment: This is the pre-proofed version. The published version will be available at http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291551-670

The Phylogeny and Function of Vocal Complexity in Geladas

The complexity of vocal communication varies widely across taxa – from humans who can create an infinite repertoire of sound combinations to some non-human species that produce only a few discrete sounds. A growing body of research is aimed at understanding the origins of ‘vocal complexity’. And yet, we still understand little about the evolutionary processes that led to, and the selective advantages of engaging in, complex vocal behaviors. I contribute to this body of research by examining the phylogeny and function of vocal complexity in wild geladas (Theropithecus gelada), a primate known for its capacity to combine a suite of discrete sound types into varied sequences. First, I investigate the phylogeny of vocal complexity by comparing gelada vocal communication with that of their close baboon relatives and with humans. Comparisons of vocal repertoires reveal that geladas – specifically the males – produce a suite of unique or ‘derived’ call types that results in a more diversified vocal repertoire than baboons. Also, comparisons of acoustic properties reveal that geladas produce vocalizations with greater spectro-temporal modulation, a feature shared with human speech, than baboons. Additionally, I show that the same organizational principle – Menzerath’s law – underpins the structure of gelada vocal sequences (i.e., combinations of derived and homologous call types) and human sentences. Second, I investigate the function of vocal complexity by examining the perception of male complex vocal sequences (i.e., those with more derived call types), the contexts in which they are produced, and how their production differs across individuals. A playback experiment shows that female geladas perceive ‘complex’ and ‘simple’ vocal sequences as being different. Then, two observational studies show that male production of complex vocal sequences mediates their affiliative interactions with females, both during neutral periods and periods of uncertainty (e.g., following conflicts). Finally, I find evidence that vocal complexity can act as a signal of male ‘quality’, in that more dominant males exhibit higher levels of vocal complexity than their subordinate counterparts. Collectively, the work presented in this dissertation presents an integrative investigation of the ultimate origins of complex communication systems, and in the process, it highlights the critical importance of approaching the study of complexity from several scientific perspectives.PHDPsychologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138479/1/gustison_1.pd

The challenges of statistical patterns of language: the case of Menzerath's law in genomes

The importance of statistical patterns of language has been debated over decades. Although Zipf's law is perhaps the most popular case, recently, Menzerath's law has begun to be involved. Menzerath's law manifests in language, music and genomes as a tendency of the mean size of the parts to decrease as the number of parts increases in many situations. This statistical regularity emerges also in the context of genomes, for instance, as a tendency of species with more chromosomes to have a smaller mean chromosome size. It has been argued that the instantiation of this law in genomes is not indicative of any parallel between language and genomes because (a) the law is inevitable and (b) noncoding DNA dominates genomes. Here mathematical, statistical, and conceptual challenges of these criticisms are discussed. Two major conclusions are drawn: the law is not inevitable and languages also have a correlate of noncoding DNA. However, the wide range of manifestations of the law in and outside genomes suggests that the striking similarities between noncoding DNA and certain linguistics units could be anecdotal for understanding the recurrence of that statistical law.Peer Reviewe